O-ring, 68 x 3.5 mm – Buna, Part# 23950121 – vacstellar

This is a round rubber ring – simple but very important.

It measures 68 mm inside diameter and 3.5 mm thick. The material is Buna (also called Nitrile), which works great with oil and handles normal pump temperatures well.

It fits on the bigger Leybold Trivac pumps: D40B, D65B, S40B, S65B, D40BCS, and D65BCS.

 this O-ring used in places like the oil housing, end covers, or other sealing spots. It squeezes between two metal parts to make an airtight seal. That keeps oil inside and air outside so your pump holds vacuum and doesn’t leak.

Over time rubber can get hard, crack, or flatten. When that happens, you start seeing oil spots or the pump struggles to pull a good vacuum.